8.1.1 State that thermal energy may be completely converted to work in a single process, but that a continuous conversion of this energy into work requires a cyclical process an the transfer of some energy from the system. 8.1.2 Explain what is meant by degraded energy Students should understand that, in any process that involves energy transformations, the energy that is transferred to the surroundings (thermal energy) is no longer available to produce useful work.
Energy can be converted from one form to another. The total sum of energy at the start is always equal to sum of the total energy at the end. But some energy is converted to forms that is not useful. The useless energy is said to have "degraded". High-grade energy has the potential to do a lot of useful work, while low-grade energy does not.
Example:
When a car engine operates, uses the chemical energy in gasoline. Some of this energy is transferred to the engine pistons as kinetic energy (useful energy) while most of it is lost as heat (degraded, useless energy).
8.1.3 Construct and analyse energy flow diagrams (Sankey diagrams) and identify where the energy is degraded. It is expected that students will be able to construct flow diagrams for various systems including those described in sub-topics 8.3 and 8.4
A Sankey diagram is a diagram that visually shows energy transfer that can be used to analyze energy degradation.The thickness of the arrows shows the amount of energy transfer.
Example:
More complicated than the one in our green book, but shows the idea. Got this from sankey-diagrams.com.
174PW of solar radiation comes to earth (orange). It is reflected by various things like the atmosphere, clouds, etc. etc. Some of the heat from earth also radiated into space (yellow). Radiation from the earth is first absorbed by the atmosphere, then emitted into space. Pretty simple. Just follow the arrows, and the size of the arrows represent the amount of energy :D
8.1.4 Outline the principal mechanisms in the production of electrical power. Students should know that electrical energy may be produced by rotating coils in a magnetic field. In sub-topics 8.2 and 8.3, students look into more detail at energy sources used to provide the energy to rotate the coils.
8.1 Energy degradation and power generation
2 hours8.1.1 State that thermal energy may be completely converted to work in a single process, but that a continuous conversion of this energy into work requires a cyclical process an the transfer of some energy from the system.
8.1.2 Explain what is meant by degraded energy
Students should understand that, in any process that involves energy transformations, the energy that is transferred to the surroundings (thermal energy) is no longer available to produce useful work.
Energy can be converted from one form to another. The total sum of energy at the start is always equal to sum of the total energy at the end. But some energy is converted to forms that is not useful. The useless energy is said to have "degraded". High-grade energy has the potential to do a lot of useful work, while low-grade energy does not.
Example:
When a car engine operates, uses the chemical energy in gasoline. Some of this energy is transferred to the engine pistons as kinetic energy (useful energy) while most of it is lost as heat (degraded, useless energy).
8.1.3 Construct and analyse energy flow diagrams (Sankey diagrams) and identify where the energy is degraded.
It is expected that students will be able to construct flow diagrams for various systems including those described in sub-topics 8.3 and 8.4
A Sankey diagram is a diagram that visually shows energy transfer that can be used to analyze energy degradation.The thickness of the arrows shows the amount of energy transfer.
Example:
More complicated than the one in our green book, but shows the idea. Got this from sankey-diagrams.com.
174PW of solar radiation comes to earth (orange). It is reflected by various things like the atmosphere, clouds, etc. etc. Some of the heat from earth also radiated into space (yellow). Radiation from the earth is first absorbed by the atmosphere, then emitted into space. Pretty simple. Just follow the arrows, and the size of the arrows represent the amount of energy :D
8.1.4 Outline the principal mechanisms in the production of electrical power.
Students should know that electrical energy may be produced by rotating coils in a magnetic field. In sub-topics 8.2 and 8.3, students look into more detail at energy sources used to provide the energy to rotate the coils.